This book is a tremendous tool for the DM/world-builder. Every trait in here (and there are hundreds and hundreds) comes with descriptive text written in the standard D&D tone. They all have point values so you can mix and match and have some expectation of balance. (Or know just how out of balance you're going to get.) The lore generation tips are very helpful if you want to write backgrounds from scratch, but there are also helpful random tables that cover several pages of potential background information if you need a boost.

The huge collection of example races is full-featured, with traits, backgrounds, and sometimes spells for each. There are some great NPCs at the end, spells, feats, all kinds of good stuff. This book is full of flavor!

My one recommendation: don't try to print the whole thing for use off-line, you'll use a lot of toner. I did print the random trait tables as a reference section, for use on the fly, and because they list the traits by point value, super useful for working out a species.